In this paper, the leader-following consensus problem is investigated for upper-triangular nonlinear MASs (multi-agent systems) via sampled and delayed output feedback. The sampled outputs transmitted through the communication channels are used to constructed the output feedback controllers directly. Then, the output feedback control signals transmitted through the other communication channels are used to update the MASs. Two kinds of transmission delays, i.e., transmission delays from the MASs to the output feedback controllers and transmission delays from the output feedback controllers to the MASs, make the MASs and the output feedback controllers to be updated at different time instants. A method of interval decomposition is proposed such that the MASs and the output feedback controllers are updated at the same interval. Then, sufficient conditions are presented to ensure the MASs reach leader-following consensus. At last, an example is provided to verify efficiency of the proposed methods.